1. Field of the Invention
The present invention pertains generally to feed systems that may be used for filling a bag with a particulate material and more specifically, to a filling spout for a feed system that provides for automatic weighing of the bag being filled without influencing the measurement accuracy of the bag weight.
2. Prior Art
Systems for feeding a particulate material such as fertilizer into a bag and for providing automatic weighing of the bag as it is being filled are well-known in the art. By way of example, U.S. Pat. No. 3,618,684 to Burke, et al discloses a bag filling apparatus wherein charges of material are successively weighed out by a scale and dispensed into a feed tank having a spout or nozzle upon which an empty bag is mounted. Similarly, U.S. Pat. No. 3,474,836 to Schwake, et al discloses a bag filling machine for handling bulk materials and in which the material to be packed is automatically weighed and then run through a funnel conduit into the bag which is held upon the discharge spout of the funnel conduit. Another such example is disclosed in U.S. Pat. No. 2,705,607 to Inglett.
It is also considered conventional in the prior art to provide a bag filling machine having means for automatic weighing of the bag contents utilizing feed mechanisms such as an auger feed screw, impeller, or pneumatic device for conveying the particulate material through a filling tube into the bag. In an auger feed screw bag filling apparatus it is well-known to provide a second tube outside of and coaxial with the auger feed screw tube which is spaced from the latter two and connected by well-known means to an automatic weighing apparatus. In such configurations the bag to be filled is, typically, placed over the weighing tube which is spaced from the filling tube to permit the bag contents to be weighed while substantially unaffected by the auger feed screw filling tube, the feed screw or any particulate material still in the auger feed tube that has not yet entered the bag and should therefore not contribute to the measured weight. In such prior art configurations it has become well-known to provide means for sealing the cylindrical space between the filling tube and the weighing tube to prevent the accumulation of particulate material therein which would otherwise inadvertently affect the weight measurement rendering the bag weighing process less accurate. In order to provide the aforementioned seal, prior art devices of the type described normally utilize an annularly-shaped resilient material such as neoprene which, as will be seen hereinafter, is commonly glued or otherwise affixed to the respective facing surfaces of the weighing tube and filling tube adjacent the exits thereof to prevent the flow of particulate material into the aforementioned space therebetween. Until recently this was believed to be a satisfactory solution to the aforementioned problem of inaccurate weighing of bags being filled by an auger feed screw feed system.
More recently however, particularly with the advent of extremely accurate and precise electronic weighing systems such as those that use load cells and microprocessor controlled electronic circuitry, it has been found that although the aforementioned prior art seal does not permit the particulate material to accumulate between the tubes and thereby detrimentally affect the accuracy of the weighing process, the resiliency of the seal itself provides an inadvertent spring affect between the tubes which tends to resist the movement of the weighing tube and thereby results in a lower measured weight than the actual weight of the bag contents. Therefore, the aforementioned resilient seal of the prior art prevents one source of bag weighing inaccuracy but only by creating a second such source which still prevents a truly accurate weight measurement of the bag contents while the bag is being filled by an auger feed screw or other type of feed system.